Gilbert du Motier, Marquis de Lafayette was an aristocratic French military officer who fought on behalf of the United States during the American Revolution. He was also a major figure in the French Revolution.
There are quite a few references on-line regarding his hair colour;
Lafayette had red hair and a long nose.Lafayette by Joann A. Grote
Gilbert was tall and had red hair.Marquis de Lafayette by Gregory Payan
And the following quite lucid description from a book published in the 19th century;
At this period of his life, the Marquis de Lafayette was a noble looking man, notwithstanding his deep red hair. His forehead, though receding, was fine, his eye clear hazel, and his mouth and chin delicately formed; exhibiting beauty rather than strength.http://quod.lib.umich.edu/m/moa/AAM7015.0001.001?rgn=main;view=fulltext
The painting below of Lafayette, along with his son, George Washington Lafayette, shows them both with rather fair, reddish hair.